| Message ID | 20210713140612.2721113-5-Rodrigo.Siqueira@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/amd/display: Base changes for isolating FPU operation in a single place | expand |
Am 13.07.21 um 16:06 schrieb Rodrigo Siqueira: > To fully isolate FPU operations in a single place, we must avoid > situations where compilers spill FP values to registers due to FP enable > in a specific C file. Note that even if we isolate all FPU functions in > a single file and call its interface from other files, the compiler > might enable the use of FPU before we call DC_FP_START. Nevertheless, it > is the programmer's responsibility to invoke DC_FP_START/END in the > correct place. To highlight situations where developers forgot to use > the FP protection before calling the DC FPU interface functions, we > introduce a helper that checks if the function is invoked under FP > protection. If not, it will trigger a kernel warning. > > Changes since V1: > - Remove fp_enable variables > - Rename dc_is_fp_enabled to dc_assert_fp_enabled > - Replace wrong variable type > > Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com> > --- > .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 22 +++++++++++++++++++ > .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h | 1 + > .../drm/amd/display/dc/dcn20/dcn20_resource.c | 2 ++ > .../drm/amd/display/dc/fpu_operations/dcn2x.c | 17 ++++++++++++++ > 4 files changed, 42 insertions(+) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c > index 73179e9e859a..74153a2816f9 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c > @@ -41,6 +41,28 @@ > > static DEFINE_PER_CPU(int, fpu_recursion_depth); > > +/** > + * dc_assert_fp_enabled - Check if FPU protection is enabled > + * > + * This function tells if the code is already under FPU protection or not. A > + * function that works as an API for a set of FPU operations can use this > + * function for checking if the caller invoked it after DC_FP_START(). For > + * example, take a look at dcn2x.c file. > + * > + * Return: > + * Return true if we already enabled FPU protection, otherwise return false. > + */ > +inline bool dc_assert_fp_enabled(void) Assert indicates that you print a warning if the condition isn't meet, but you only return the condition. Either rename the function or raise the warning directly. > +{ > + int *pcpu, depth = 0; > + > + pcpu = get_cpu_ptr(&fpu_recursion_depth); > + depth = this_cpu_read(fpu_recursion_depth); > + put_cpu_ptr(&fpu_recursion_depth); Again this doesn't make sense. Either you use this_cpu_read() or your use get_cpu_ptr()/put_cpu_ptr(), but not both. > + > + return depth > 1; > +} > + > /** > * dc_fpu_begin - Enables FPU protection > * @function_name: A string containing the function name for debug purposes > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h > index fb54983c5c60..97941794b77c 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h > @@ -27,6 +27,7 @@ > #ifndef __DC_FPU_H__ > #define __DC_FPU_H__ > > +bool dc_assert_fp_enabled(void); > void dc_fpu_begin(const char *function_name, const int line); > void dc_fpu_end(const char *function_name, const int line); > > diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c > index f99b09643a52..d0b34c7f99dc 100644 > --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c > +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c > @@ -2355,7 +2355,9 @@ int dcn20_populate_dml_pipes_from_context( > } > > /* populate writeback information */ > + DC_FP_START(); > dc->res_pool->funcs->populate_dml_writeback_from_context(dc, res_ctx, pipes); > + DC_FP_END(); > > return pipe_cnt; > } > diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c > index c815d6c01d64..d8183da0c2b0 100644 > --- a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c > +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c > @@ -41,6 +41,22 @@ > * that deals with FP register is contained within this call. > * 3. All function that needs to be accessed outside this file requires a > * public interface that not uses any FPU reference. > + * 4. Developers should not use DC_FP_START/END in this file, but they need to This needs to be harder, e.g. "Developers must not use....". Regards, Christian. > + * ensure that the caller invokes it before access any function available in > + * this file. For this reason, public API in this file must invoke > + * ASSERT(dc_assert_fp_enabled()); > + * > + * Let's expand a little bit more the idea in the code pattern number for. To > + * fully isolate FPU operations in a single place, we must avoid situations > + * where compilers spill FP values to registers due to FP enable in a specific > + * C file. Note that even if we isolate all FPU functions in a single file and > + * call its interface from other files, the compiler might enable the use of > + * FPU before we call DC_FP_START. Nevertheless, it is the programmer's > + * responsibility to invoke DC_FP_START/END in the correct place. To highlight > + * situations where developers forgot to use the FP protection before calling > + * the DC FPU interface functions, we introduce a helper that checks if the > + * function is invoked under FP protection. If not, it will trigger a kernel > + * warning. > */ > > static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc, > @@ -83,5 +99,6 @@ static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc, > void dcn20_populate_dml_writeback_from_context(struct dc *dc, > struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes) > { > + ASSERT(dc_assert_fp_enabled()); > _dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes); > }
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c index 73179e9e859a..74153a2816f9 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c @@ -41,6 +41,28 @@ static DEFINE_PER_CPU(int, fpu_recursion_depth); +/** + * dc_assert_fp_enabled - Check if FPU protection is enabled + * + * This function tells if the code is already under FPU protection or not. A + * function that works as an API for a set of FPU operations can use this + * function for checking if the caller invoked it after DC_FP_START(). For + * example, take a look at dcn2x.c file. + * + * Return: + * Return true if we already enabled FPU protection, otherwise return false. + */ +inline bool dc_assert_fp_enabled(void) +{ + int *pcpu, depth = 0; + + pcpu = get_cpu_ptr(&fpu_recursion_depth); + depth = this_cpu_read(fpu_recursion_depth); + put_cpu_ptr(&fpu_recursion_depth); + + return depth > 1; +} + /** * dc_fpu_begin - Enables FPU protection * @function_name: A string containing the function name for debug purposes diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h index fb54983c5c60..97941794b77c 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h @@ -27,6 +27,7 @@ #ifndef __DC_FPU_H__ #define __DC_FPU_H__ +bool dc_assert_fp_enabled(void); void dc_fpu_begin(const char *function_name, const int line); void dc_fpu_end(const char *function_name, const int line); diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c index f99b09643a52..d0b34c7f99dc 100644 --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c @@ -2355,7 +2355,9 @@ int dcn20_populate_dml_pipes_from_context( } /* populate writeback information */ + DC_FP_START(); dc->res_pool->funcs->populate_dml_writeback_from_context(dc, res_ctx, pipes); + DC_FP_END(); return pipe_cnt; } diff --git a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c index c815d6c01d64..d8183da0c2b0 100644 --- a/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c +++ b/drivers/gpu/drm/amd/display/dc/fpu_operations/dcn2x.c @@ -41,6 +41,22 @@ * that deals with FP register is contained within this call. * 3. All function that needs to be accessed outside this file requires a * public interface that not uses any FPU reference. + * 4. Developers should not use DC_FP_START/END in this file, but they need to + * ensure that the caller invokes it before access any function available in + * this file. For this reason, public API in this file must invoke + * ASSERT(dc_assert_fp_enabled()); + * + * Let's expand a little bit more the idea in the code pattern number for. To + * fully isolate FPU operations in a single place, we must avoid situations + * where compilers spill FP values to registers due to FP enable in a specific + * C file. Note that even if we isolate all FPU functions in a single file and + * call its interface from other files, the compiler might enable the use of + * FPU before we call DC_FP_START. Nevertheless, it is the programmer's + * responsibility to invoke DC_FP_START/END in the correct place. To highlight + * situations where developers forgot to use the FP protection before calling + * the DC FPU interface functions, we introduce a helper that checks if the + * function is invoked under FP protection. If not, it will trigger a kernel + * warning. */ static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc, @@ -83,5 +99,6 @@ static noinline void _dcn20_populate_dml_writeback_from_context(struct dc *dc, void dcn20_populate_dml_writeback_from_context(struct dc *dc, struct resource_context *res_ctx, display_e2e_pipe_params_st *pipes) { + ASSERT(dc_assert_fp_enabled()); _dcn20_populate_dml_writeback_from_context(dc, res_ctx, pipes); }
To fully isolate FPU operations in a single place, we must avoid situations where compilers spill FP values to registers due to FP enable in a specific C file. Note that even if we isolate all FPU functions in a single file and call its interface from other files, the compiler might enable the use of FPU before we call DC_FP_START. Nevertheless, it is the programmer's responsibility to invoke DC_FP_START/END in the correct place. To highlight situations where developers forgot to use the FP protection before calling the DC FPU interface functions, we introduce a helper that checks if the function is invoked under FP protection. If not, it will trigger a kernel warning. Changes since V1: - Remove fp_enable variables - Rename dc_is_fp_enabled to dc_assert_fp_enabled - Replace wrong variable type Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com> --- .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c | 22 +++++++++++++++++++ .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.h | 1 + .../drm/amd/display/dc/dcn20/dcn20_resource.c | 2 ++ .../drm/amd/display/dc/fpu_operations/dcn2x.c | 17 ++++++++++++++ 4 files changed, 42 insertions(+)